As is well known, selected electric or electronic parts radiate electromagnetic waves which can cause noise or unwanted signals to appear in electric or electronic parts and devices existing in the vicinity of the radiating parts. Accordingly, it is highly desirable to provide shielding and/or grounding for electronic components that use circuitry that emits or is susceptible to electromagnetic radiation. It is known that these components can be shielded to reduce undesirable electromagnetic interference and/or susceptibility effects with the use of a conductive shield that reflects or dissipates the electromagnetic charges and fields. Such shielding may be grounded to allow the offending electrical charges and fields to be dissipated without disrupting the operation of the electronic components enclosed within the shield.
Various types of EMI/RFI shielding devices are known for reducing the transmission of EMI and RFI. Among the known devices are gaskets or strips of a resiliently deformable material which are secured to an openable, movable, or removable access panel, door, drawer, or the like (hereinafter "door"), to block the transmission of EMI/RFI through the small clearance between the door and the adjacent structure which forms the opening into and out of which the door is movable. Such strips are useful for shielding openings of housings for electronic components which are highly sensitive to the adverse effects of EMI/RFI.
Such known devices are typically made of one of several materials which have the combined functions of acting as an EMI/RFI shield, and which are resiliently deformable so that they can be compressed between the door when closed, and will spring back to an uncompressed configuration when the door is moved out of the opening. U.S. patent application Ser. No. 08/819,983, filed Mar. 18, 1997, entitled "SELF-TERMINATING, KNITTED METALIZED YARN EMI/RFI SHIELDING GASKET," now U. S. Pat. No. 5,889,299 which is hereby incorporated by reference, provides examples of such gaskets.
One difficulty with known gaskets for providing EMI/RFI shielding is that the gasket material, while resilient, is not as compressible and resilient as other materials. The reduced compressibility sometimes makes it difficult for the gasket to provide a proper environmental shield, and the reduced resilience sometimes makes it difficult for the gasket to spring back into its original shape when compression on the gasket is removed. It is desirable to provide a gasket that combines high levels of EMI/RFI shielding with high compressibility and resilience characteristics to provide high levels of environmental shielding.
Another problem with EMI/RFI shielding gaskets is that conductive elastomers tend to be expensive as compared to other gasket materials. It is desirable to provide a gasket that is inexpensive and simple to install.
In accordance with one aspect of the present invention, a gasket is provided that includes an elongated strip including a first resilient gasket component and a second resilient gasket component having shielding properties, the first and second gasket components being joined together.
In accordance with another aspect of the present invention, a method for making a gasket is disclosed. According to the method, a first resilient gasket component is formed, a second resilient gasket component, the second gasket component having shielding properties is formed, and the first gasket component to the second gasket component are joined.
In accordance with yet another aspect of the present invention, a gasket is provided that includes an elongated strip including a first resilient gasket component and a second resilient gasket component of a different material than the first gasket component, the first and second gasket components being joined together.